1. Field of the Invention
This invention relates to a mimeographic printing machine which has a printing drum to be driven to rotate with a mimeographic stencil wound on its outer circumferential surface and in which ink supplied from the inside the master drum is transferred to successive print sheets one at a time through pores of the mimeographic stencil.
2. Description of the Related Art
Many of modern printers or the like are equipped with a sorter for automatically sorting printed sheets which have been discharged from the printer, individually into a plurality of bins (receptacles). At the start of printing, the user may select any of the following facilities:
(1) The group sort mode, in which a number of printed sheets for each of pages of an original document will be received collectively on a respective bin.
(2) The sort mode, in which a number of printed sheets for each of pages of an original document will be received consecutively on the respective bins in the order of paging of an original document; that is, a set of printed sheets for all of the pages of the original document will be received on every bin in the order of paging of the original document.
(3) The non-sort mode, in which all of printed sheets will be received directly on a discharge tray, without using the sorter. This mode is used for a trial print or mass print.
However, in the mimeographic printing machine, ink is forced through fine pores of the mimeographic stencil from one side to the other of the stencil by the pressure means, which is situated outside the master drum, to attached onto a sheet during the printing. If the non-sort mode of (3) above is selected, before the ink attached to the preceding printed sheet has not yet been dried up, the succeeding print sheet is placed over this preceding one so that the ink on the previous printed sheet would be transferred to the back surface of the next sheet, which is so called a back transfer phenomenon.
For preventing such back transfer phenomenon, it has been a common practice to insert unprinted sheets one by one between successive printed sheets. But this inserting have to be done in conformity to the sheet discharge speed of the mimeographic printing machine, and after the printing, these inserted unprinted sheets have to be removed, which is laborious and time-consuming.
In another conventional attempt, a drier was used inside or outside the mimeographic printing machine. The whole system would be bulk and would be difficult to secure safety as the drier was in the form of a hot air blower or heat rollers, thus resulting in an increased cost of production.